1. Field of the Invention
The present invention is related to a method of determining transit power for data transmission between a network and a user equipment and related wireless communication system, and more particularly, to a method of determining transit power for data transmission between a network and a user equipment by automatically using an extrapolation formula and an interpolation formula for computing E-DPDCH gain factor and related wireless communication system.
2. Description of the Prior Art
The 3rd Generation Partnership Project (3GPP) has developed various wireless communication networks. A universal mobile telecommunications system (UMTS) is a 3rd generation (3G) network which adopts a wideband code division multiple access (WCDMA) technology capable of providing high frequency spectrum utilization, universal coverage, and high-speed/quality multimedia data transmission. In the UMTS network, a radio access network known as a universal terrestrial radio access network (UTRAN) includes multiple base stations, commonly known as Node-Bs (NBs), for communicating with multiple user equipment (UE). A long-term evolution (LTE) system is a 4th generation (4G) network which includes a new radio interface and radio network architecture capable of providing a high data rate, low latency, packet optimization, and improved system capacity and coverage. In the LTE network, a radio access network known as an evolved UTRAN (E-UTRAN) includes multiple evolved NBs (eNBs) for communicating with multiple UEs and a core network which includes a mobility management entity (MME), a serving gateway and other devices for NAS (Non Access Stratum) control.
A UE may communicate with a wireless communication network using various channels. In the UMTS network, an enhanced dedicated channel (E-DCH) has been introduced in the uplink transmission. The E-DCH is associated with an enhanced dedicated physical data channel (E-DPDCH) and an enhanced dedicated physical control channel (E-DPCCH). During registration, the UE and the network may exchange capability lists, each of which allows the recipient entity (the UE or the network) to know which capabilities the sending entity (the network or the UE) supports and thus which capabilities and features may be invoked and used for various services.
The UE and the network are required to operate according to 3GPP specifications which are structured as various release versions. Additional capabilities or modified functions are made available in each newer release version of 3GPP specifications. Existing 3GPP specifications fail to include the consistency of certain features, such as power interpolation/extrapolation. For example, the network may send a RADIO BEARER RECONFIGURATION message to instruct the UE to use an interpolation formula when calculating the gain factor of the E-DPDCH. Later, the network may send an ACTIVE SET UPDATE message to update the active set of the connection between the UE and the network. If the ACTIVE SET UPDATE message does not include any information about power interpolation/extrapolation, the UE detects this inconsistency and thus uses an extrapolation formula when calculating the gain factor of the E-DPDCH. Under such circumstance, radio link failure may occur when the UE uses an inappropriate gain factor for data transmission.